In recent years, membrane separation technology has been used in the field of processing a large amount of fluid, such as gas separation and city water treatment, due to the advantage in terms of low initial cost. In particular, apparatuses including a separation element disposed in a casing are used, and the separation element is typically made from a ceramic material because a ceramic separation element has advantages such as being easy to clean, being durable, and so on.
The separation element includes a membrane, a supporter of the membrane, a channel member and so on that are integrated with each other, while the shape of the separation element may vary depending on the purpose of separation.
A gas separation apparatus has been disclosed (in Patent Document 1 described later) that includes a gas separator (corresponding to the above “separation element”) having a gas separation membrane, which allows only a specific gas component to pass therethrough, disposed on a surface of a porous base member. When separating a high-temperature gas, the closeness of contact between the gas separator and a fixing member for fixing the gas separator may become insufficient due to thermal expansion of the gas separator and the fixing member, and thereby gas leakage may occur. If such gas leakage occurs, a specific gas component that has passed through the gas separation membrane may become mixed with residual gas components, so that the specific gas component cannot be efficiently separated.
To prevent this, the gas separation apparatus disclosed in Patent Document 1 includes a gas separator, a container having a recess in which the gas separator is contained, a seal member disposed in the gap between the outer peripheral surface of the gas separator and a side wall, and a clamping member that clamps and presses the seal member in an axial direction in the gap. The ratio of the thermal expansion coefficient of the container to that of the gas separator is in the range of 0.55 to 0.95, so that the occurrence of gas leakage from a joint portion between the gas separator and a member that immovably holds the gas separator is suppressed.
The flow rate of a fluid that passes through a fluid separation membrane is limited to a certain range for the purpose of realizing desired separation ability. The higher the separation processing flow rate, the larger the membrane area needed. Therefore, although a single separation element can be used as a unit, in a case of processing a large amount of water in a water treatment plant or processing a large amount of fluid for gas separation, a large number of separation elements are serially arranged so as to increase the membrane area and improve the separation capability.
For this purpose, a fluid separation apparatus has been disclosed that includes a plurality of separation elements, each of which is contained in a corresponding one of casings that are serially connected to each other using flanges, so as to increase the filtration area and increase the water separation capability (Patent Document 2 described below).